My 7-year-old daughter is learning music notation at school. (Thankfully.) She told me today that they are taught to draw the crotchet rest as "a Z with a C below", which was a novel idea to me, though pleasing enough.

As a result of which, I'm now having to research the origins of that form of rest....

A good image. Checking my own very quickly-without-thinking hand-written crotchet rests, they seem to be a Z drawn from the top at 20º from vertical continuing into a C at 0º below. A “Z with a C below” seems pretty close and a very clever way for a young child to remember how to draw the rest.

As a result of which, I'm now having to research the origins of that form of rest....

You may find that the quarter rest has as many variations as the treble clef, maybe even more. I have always found it to be the most difficult musical symbol to draw by hand so that it looks like an engraved symbol. Perhaps for that reason and because they are used so frequently, many composers have done a simple v- or z-shaped affair that lies somewhat horizontally along a staff line rather than more vertical one that we see in engraved music. Almost anything seems to be acceptable, as long as it is easily distinguishable from an eighth rest. The reverse eighth rest as a quarter rest was thus doomed from the start.

The quarter (semiminima) rest started as a reversed eighth (fusa) rest in white mensural notation, didn’t it? So it would be interesting to know when the form was first used.

...which illustrates once again why someone needs to write a book showing the evolution of every aspect of the notational system used in Western music. It would truly illustrate the "survival of the fittest" and why productive innovation is somewhat rare.